Abstract
Recently, we have identified multipotent stem cell populations residing in the interstitial spaces of skeletal muscle. We characterized these cells using FACS on the basis of cell surface antigen expression, and sorted them as a CD34+/45- and CD34-/45- cell fractions from enzymatically isolated cells. Cells in the CD34+/45- fraction (designated Sk-34 cells) were >94% positive for Sca-1 and mostly negative (<3% positive) for CD14, 31, 49, 144, c-kit and FLK-1showing that Sk-34 cells are not committed endothelial progenitors. However, Sk-34 cells formed colonies in clonal cell culture, and CFU displayed the potential to differentiate into adipocytes, endothelial, and myogenic cells. We also identified cells in the CD34-/45- (designated Sk-DN cells) fraction as a putative cell population that includes further immature stem cells; that can form clonal sphere-like colonies in a collagen based cell culture with bFGF and EGF; and that exhibits the potential to differentiate into myogenic and endothelial cells. In addition, the Sk-34 and Sk-DN cells included only a few side-population (SP) cells and mostly composed by main-population cells (1:1000). These findings demonstrated that multipotent stem cells (Sk-34 and Sk-DN cells) residing in the interstitial spaces of skeletal muscle, and potentially contribute to postnatal myogenesis and vasculogenesis following muscle growth and/or muscle hypertrophy, and there were not SP cells. [J Physiol Sci. 2006;56 Suppl:S145]
